A vessel has $N_2$ gas and water vapours at a total pressure of 1 atm. The partial pressure of water vapours is 0.3 atm. The contents of this vessel are transferred to another vessel having one-third of the capacity of original volume, completely at the same temperature the total pressure of this system in the new vessel is

${{\mathrm{P}}^{\text{'}}}_{{\mathrm{N}}_2}+{{\mathrm{P}}^{\text{'}}}_{{\mathrm{H}}_2\mathrm{O}}=1\mathrm{atm}$

${{\mathrm{P}}^{\text{'}}}_{{\mathrm{H}}_2\mathrm{O}}=0.3\mathrm{atm}$

${{\mathrm{P}}^{\text{'}}}_{{\mathrm{N}}_2}=0.7\mathrm{atm}$

Now new pressure of ${\mathrm{N}}_2$ in another vessel of volume V/3 at same temperature T is given by

${{\mathrm{P}}^{\text{'}\text{'}}}_{{\mathrm{N}}_2}\times \frac{\mathrm{V}}{3}=0.7\mathrm{V}$

$\therefore {{\mathrm{P}}^{\text{'}\text{'}}}_{{\mathrm{N}}_2}=2.1\mathrm{atm}$

Since aqueous tension remains constant, and thus total pressure in new vessel

                                                               $={{\mathrm{P}}^{\text{'}\text{'}}}_{{\mathrm{N}}_2}+{{\mathrm{P}}^{\text{'}}}_{{\mathrm{H}}_2\mathrm{O}}=2.1+0.3=2.4\mathrm{atm}$